Relationship between upper and lower limb function, cognitive impairment, and depression in patients with chronic obstructive pulmonary disease: A cross-sectional study.

Chronic obstructive pulmonary disease (COPD) often coexists with limb dysfunction, cognitive decline, and depression. The 20-item Upper Extremity Functional Index (UEFI) and Lower Extremity Functional Index (LEFI) (each 0-80, higher = better) are COPD-specific, yet their links to cognition and mood remain untested. We assessed whether UEFI and LEFI independently predict cognitive impairment and clinically significant depressive symptoms. In this single-center cross-sectional study (January 2021-January 2023), 120 stable out-patients aged ≥40 years with spirometry-confirmed COPD and without confounding neuromuscular disorders were enrolled. Upper and lower limb functions were assessed using the UEFI and LEFI, respectively. Cognitive impairment was defined as a Montreal Cognitive Assessment score < 26; moderate-to-severe depression as a Patient Health Questionnaire-9 score ≥ 10. Both instruments are validated in COPD. Multivariable logistic regression adjusted for age, sex, body mass index, smoking status, forced expiratory volume in 1 second/forced vital capacity ratio, and global initiative for chronic obstructive lung disease stage. Participants (mean age 65.2 ± 7.8 years; 58.3% male) included 35.8% with depression and 29.2% with cognitive impairment. Each 1-standard deviation increase in UEFI reduced the odds of cognitive impairment (adjusted odds ratio: 0.46; 95% confidence interval [CI] 0.31-0.70) and depression (odds ratio: 0.48; 95% CI: 0.30-0.76); corresponding LEFI estimates were 0.65 (95% CI: 0.47-0.90) and 0.51 (95% CI: 0.35-0.74). Associations persisted across sensitivity analyses. Poor self-reported limb function independently predicts cognitive decline and depression in COPD. Incorporating UEFI/LEFI into routine assessment may enable early detection and guide integrated rehabilitation.